U.S. patent number 7,887,032 [Application Number 12/266,297] was granted by the patent office on 2011-02-15 for self-centering control rod.
This patent grant is currently assigned to Fallbrook Technologies Inc.. Invention is credited to Curtis W Malone.
United States Patent |
7,887,032 |
Malone |
February 15, 2011 |
Self-centering control rod
Abstract
Embodiments include a self-centering control rod device having
two independently operating springs, a bushing, and a control rod.
The two springs utilize preload compression to maintain the control
rod centered. One spring operates directly against the control rod
while the other operates against the bushing. Each spring may have
different spring strength or established preload in order to
balance out the application force required to control a particular
object. Spring compression force adjustments on one spring do not
affect the center point or the spring compression force adjustment
of the other spring.
Inventors: |
Malone; Curtis W (Mustang,
OK) |
Assignee: |
Fallbrook Technologies Inc.
(San Diego, CA)
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Family
ID: |
40586810 |
Appl.
No.: |
12/266,297 |
Filed: |
November 6, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090114058 A1 |
May 7, 2009 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60986159 |
Nov 7, 2007 |
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Current U.S.
Class: |
267/70;
74/592 |
Current CPC
Class: |
G05G
23/02 (20130101); G05G 5/05 (20130101); Y10T
74/2158 (20150115) |
Current International
Class: |
F16F
9/00 (20060101) |
Field of
Search: |
;267/66-74 ;74/592 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schwartz; Christopher P
Attorney, Agent or Firm: Knobbe, Martens, Olson & Bear
LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Patent
Application No. 60/986,159, filed on Nov. 7, 2007, which is hereby
incorporated by reference in its entirety.
Claims
What is claimed is:
1. A self-centering control rod apparatus for maintaining a control
rod in an equilibrium position when no external operating forces
are applied, the apparatus comprising: a first and second support
bracket, each with a collinear opening; a bushing supported by the
first and second support bracket openings such that the bushing
passes through both support bracket openings and linearly
translates relative to the support brackets, the bushing
comprising: an axial centrally located opening through which the
control rod linearly translates relative to the bushing; and a
first and second spring preload device, each preload device
positively retained by the bushing, wherein the first spring
preload device is located on one end of the bushing outside of the
space between the brackets while the second spring preload device
is located near the center of the bushing in the space between the
brackets; a first spring attached to the control rod by an
attaching means on the end outside of the first bracket, wherein
the spring end opposite the attaching means abuts the first spring
preload device, and wherein the spring is partially compressed
between the attaching means and the first spring preload device; a
second spring, wherein one end of the second spring abuts the first
bracket on the inside of the first bracket and the other end of the
second spring abuts the second preload device, and wherein the
second spring is partially compressed between the first bracket and
the second spring preload device; and a travel stop device retained
by the control rod such that the travel stop device maintains
contact with the bushing, at the bushing end opposite that of the
first spring preload device and outside the first support bracket,
when no external operator forces are applied.
2. The device of claim 1, wherein at least on of the first and
second spring preload devices is adjustable.
3. The device of claim 1, wherein at least on of the first and
second spring preload devices is fixed.
4. The device of claim 1, wherein the attaching means is
adjustable.
5. The device of claim 1, wherein the attaching means is fixed.
6. The device of claim 1, wherein the travel stop is
adjustable.
7. The device of claim 1, wherein the travel stop is fixed.
8. A self-centering control rod apparatus for maintaining a control
rod in an equilibrium position when no external operating forces
are applied, the apparatus comprising: a support bracket, wherein
the support bracket has a first and second support area, each
support area separated by a distance and having an opening with
both openings collinear; a bushing supported by the first and
second support area openings such that the bushing passes through
both openings and linearly translates relative to the support
bracket, the bushing comprising: an axial centrally located opening
through which the control rod linearly translates relative to the
bushing; and a first and second spring preload device, each preload
device positively retained by the bushing, wherein the first spring
preload device is locate on one end of the bushing outside of the
space between the first and second support areas while the second
preload device is located near the center of the bushing in the
space between the first and second support areas; a first spring
attached to the control rod by an attaching means on the end
outside of the bracket, wherein the spring end opposite the
attaching means abuts the first spring preload device, and wherein
the spring is partially compressed between the attaching means and
the first spring preload device; a second spring, wherein one end
of the second spring abuts the bracket on the first support area in
the space between the first and second support areas and the other
end of the second spring abuts the second spring preload device,
and wherein the second spring is partially compressed between the
bracket and the second spring preload device; and a travel stop
device retained by the control rod such that the travel stop device
maintains contact with the bushing, at the bushing end opposite
that of the first spring preload device and outside the support
bracket, when no external operator forces are applied.
9. The device of claim 8, wherein at least one of the first and
second spring preload devices is adjustable.
10. The device of claim 8, wherein at least one of the first and
second spring preload devices is fixed.
11. The device of claim 8, wherein the attaching means is
adjustable.
12. The device of claim 8, wherein the attaching means is
fixed.
13. The device of claim 8, wherein the travel stop is
adjustable.
14. The device of claim 8, wherein the travel stop is fixed.
15. A method of maintaining a control rod in an equilibrium
position, the method comprising the steps of: operably coupling at
least one support bracket to a bushing; operably coupling a first
spring to the bushing; operably coupling a second spring to the
bushing; establishing a first spring preload on the first spring
relative to the support bracket; and establishing a second spring
preload on the second spring, wherein the first spring preload is
separate from the second spring preload.
16. The method of claim 15, wherein establishing a first spring
preload comprises providing at least one adjustable spring preload
member.
17. The method of claim 15, wherein establishing a first spring
preload comprises providing a fixed spring preload member.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a self-centering control rod
linkage that is free to move linearly yet automatically returns to
center when the actuating force is removed.
2. Description of Related Art
Certain industrial processes require a control rod mechanism that
will move freely in a linear direction (i.e., "side-to-side" or
"back-and-forth") yet return to center when the operator removes
the actuating force. For example, a typical hydraulic sliding spool
valve may be connected to a self-centering linkage. The spool valve
may have a center position with ports configured such that movement
of the spool in one direction from center opens a certain
combination of ports. Likewise, movement of the spool in the
opposite direction from center opens a different combination of
ports. At rest the spool is intended to remain in a neutral center
position.
Such a spool valve may feature a handle attached to the end of a
control rod linkage that is attached to an end of the spool. Prior
art self-centering control rod linkages (such as that depicted in
FIG. 1) typically utilize a control rod that passes through an
opening in some type of support bracket. Springs on either side of
the bracket are then attached to the control rod by either a fixed
or adjustable collar. The collar traps the spring between the face
of the collar and the bracket. With a spring and collar on both
sides of the center bracket, the spring preload force positions the
rod such that the compressed spring forces on either side of the
bracket are balanced and the rod is in a neutral position
(equilibrium).
A self-centering control rod linkage is also used in some
applications involving certain vehicle transmissions. For example,
a continuously variable transmission such as that disclosed in U.S.
Pat. No. 6,419,608 (titled "Continuously Variable Transmission" and
owned by Fallbrook Technologies) uses a self-centering control rod
to shift the transmission between its ranges
(forward-neutral-reverse). With the control rod in the center
position, the transmission is in neutral. If the control rod is
moved one direction from center, power is transferred through the
transmission such that it propels the vehicle forward. Movement of
the control rod in the opposite direction from center places the
transmission in reverse. Accordingly, a need exists for improved
self-centering control-rods.
SUMMARY
The system, method, and devices of the invention each have several
aspects, no single one of which is solely responsible for its
desirable attributes. Without limiting the scope of this invention
as expressed by the claims which follow, its more prominent
features will now be discussed briefly. After considering this
discussion, and particularly after reading the section entitled
"Detailed Description of Certain Embodiments" one will understand
how the features of this invention can provide advantages including
those described herein.
One embodiment utilizes a control rod that is partially encircled
by a bushing. The bushing is supported by two independent support
brackets (one to the left and one to the right). Both the bushing
and the control rod are free to move linearly, relative to one
another, and both relative to the brackets. Two independent
springs, one on either side of one of the brackets, provide the
force necessary to retain the control rod in the center position.
One end of the control rod is typically attached to a device to be
controlled while the other end is attached to an actuator, such as
a handgrip or lever. The springs are retained such that an operator
applying force to the actuator will cause the control rod to move
relative to the brackets. As the control rod is moved to the left
(axially), the rightmost spring is compressed and the leftmost
spring is unaffected. Conversely, as the control rod is moved to
the right the leftmost spring is compressed and the rightmost
spring is unaffected. Because only one spring is ever affected upon
moving the control rod in a given direction, each spring can
utilize different spring pressures. This allows the embodiment to
be tuned such that the operator feels a balanced force at the
actuator even if the device under control has differing
activation/deactivation force requirements.
The springs can be adjusted independently without upsetting the
center point balance. The rightmost spring contacts the control rod
at one end and contacts a preload device on the rightmost end of
the bushing, and thus acts to apply force between the control rod
and the bushing. The leftmost spring contacts one support bracket
and maintains pressure on another preload device attached to the
bushing. The spring pressure from the rightmost spring forces the
bushing interference device against a stop on the leftmost support
bracket. Thus, with no external force applied to the control rod,
the system is in this equilibrium state. Adjustments to the center
position can be made by moving the stop attached to the leftmost
support bracket.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more fully understood by reference to
the following detailed description of the preferred embodiments of
the present invention when read in conjunction with the
accompanying drawings, wherein:
FIG. 1 depicts a prior art self-centering control rod;
FIG. 2 depicts a frontal view of a preferred embodiment of the
present invention;
FIG. 3 depicts an isometric view of the same embodiment; and
FIG. 4 depicts a cutaway isometric view of the embodiment to
improve the differentiation between the various component
parts.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
The above figures are provided for the purpose of illustration and
description only, and are not intended to define the limits of the
disclosed invention. Use of the same reference number in multiple
figures is intended to designate the same or similar parts.
Furthermore, when the terms "top," "bottom," "right," "left,"
"rightward," "leftward," "first," "second," "upper," "lower"
"height" "width" "length" "end" "side" "horizontal" "vertical" and
similar terms are used herein, it should be understood that these
terms have reference only to the structure shown in the drawing and
are utilized only to facilitate describing the particular
embodiment. The extension of the figures with respect to number,
position, relationship, and dimensions of the parts to form the
preferred embodiment will be explained or will be within the skill
of the art after the following teachings of the present invention
have been read and understood.
Current self-centering control rod devices face numerous problems.
One problem is that the balance of forces on both sides of the
return mechanism is highly temperamental. This creates a system
that is difficult to establish and maintain balanced in an
equilibrium state. If the application requires any precision as to
the exact center point, virtually no drift is allowed. However,
aging and other environmental factors (such as heat) cause spring
tensions to change and the center point to shift. Current
self-centering devices must be continually calibrated to compensate
for these changes or the device may continually drift.
Another problem with current self-centering control rod devices is
the force balance required to operate the device. Such a device
must have equilibrium of force between the opposing centering
springs to remain centered. However, the valve or transmission to
which the self-centering device is attached may require a greater
force to move in one direction as opposed to the other. For
example, a spool valve may be moving against a greater fluid
pressure when moved to the right yet have very little pressure when
moving the spool to the left. With current self-centering devices,
this differing application force will be felt by the operator.
Yet another problem with current self-centering control rod devices
is the oscillations that can occur about the center point. Current
self-centering mechanisms featuring opposing compressed springs
that maintain opposing pressure on the centering bracket. However,
springs are notorious for oscillations. These spring oscillations
pass from side to side resulting in a mechanism whose center point
drifts from side to side at the frequency of oscillation.
Accordingly, a need exists for a self-centering control rod
mechanism that is simple to calibrate, maintains calibration under
environmental and operational extremes, and minimizes oscillations
about the center point. Further, a need exists for a self-centering
control rod mechanism that balances the application force felt by
the operator regardless of differing forces required by the device
under control. Embodiments disclosed herein address these needs and
others as shown herein
FIG. 2 depicts a preferred embodiment of the present invention.
This embodiment features a control rod (102) encircled by a bushing
(126). The control rod (102) and bushing (126) are free to move
linearly relative to one another. The bushing (126) passes through
openings in a leftmost support bracket (104) and a rightmost
support bracket (116). The bushing (126) is also free to move
linearly relative to the support brackets (104 and 116).
In this embodiment, the leftmost support bracket (104) features a
support area (106) with a leftward travel stop (108). This travel
stop (108) serves to maintain the position of the bushing (126)
when at rest (equilibrium). A leftmost coil spring (112) encircles
the bushing (126) and abuts the left side of the rightmost support
bracket (116). A support area (114) on this bracket serves to
maintain position on the spring (112) to keep it from contacting
the bushing (126). Threads near the center of the bushing (126)
allow for positioning of locknuts (110) to establish desired
leftmost spring (112) preload pressure. The amount of preload on
this spring (112) determines the amount of return force applied to
the control rod (102) via the bushing (126) when the control rod
(102) returns to the left upon removal of externally applied
actuating forces.
The present embodiment also features a rightmost spring (122) that
encircles the control rod (102) to the right of the rightmost
support bracket (116). In this embodiment, the end of the spring
(122) farthest from the bracket (116) is held in place on the
control rod (102) by an adjustable collar (124). This adjustable
collar (124) serves as an attaching means for attaching the spring
(122) to the control rod (102).
The side of the spring opposite the attaching means abuts a locknut
(120) placed on the rightmost end of the bushing (126). As before,
this locknut (120) serves to establish the amount of preload on the
rightmost spring (122). The amount of preload on this spring (122)
determines the amount of return force applied to the control rod
when the control rod (102) returns to the right upon removal of
externally applied actuating forces. A second adjustable collar
serves as a rightward travel stop (118) to limit the rightward
motion of the control rod (102) at rest (equilibrium).
FIG. 3 and FIG. 4 depict an isometric view of the claimed apparatus
to allow improved differentiation between the various component
parts. The cutaway view in FIG. 4 shows how the control rod (102)
passes entirely through the central portion of the bushing (126).
Further, the view shows the extent to which the bushing (126)
passes through the support brackets (104 and 116).
As stated previously, the present embodiment provides distinct,
positive stops for each direction of travel (leftward and rightward
travel stops, 108 and 118, respectively). Consequently, the
apparatus is not susceptible to oscillations about the equilibrium
point as are the prior art self-centering devices. The prior art
self-centering devices utilize balanced spring pressures on either
side of a center bracket to maintain equilibrium. Thus, the natural
harmonic oscillations generated in a spring are transferred from
one side to the other. In the present invention, the positive stops
(118 and 108) drastically reduce or prevent such transfer.
In another embodiment, the two brackets (104 and 116) are combined
into a single bracket. This single bracket, however, features two
distinct support areas (such as 106 and 114 in FIG. 2). Thus, a
single bracket may be fashioned to provide support for the claimed
apparatus. Sufficient distance is required between the support
areas to allow for movement of the leftmost spring preload device
(110).
Leftward Displacement of the Control Rod
When the control rod (102) is forced to the left, the leftward
travel stop (108) contacts the stationary support area (106). This
prevents the bushing (126) from moving to the left. This also has
the effect of maintaining the rightmost preload device (120)
stationary. The preload from the rightmost spring (122) bears
against the rightmost preload device (120) which keeps the leftward
travel stop (108) seated against the support area (106), because
the relative spacing between the rightmost preload device (120) and
the leftward travel stop (108) is fixed during device setup. Thus,
when the control rod (102) is forced to the left, the adjustable
collar (124) will compress the rightmost spring (122) in proportion
to the leftward displacement of the control rod (102). Because the
rightmost bracket (116) remains stationary as does the leftmost
preload device (110) during leftward displacement of the control
rod (102), the leftmost spring (112) remains constant and
unaffected in its preload state. When the external actuating force
is removed from the control rod (102), the increased spring
pressure in the rightmost spring (122) forces the control rod (102)
back until the rightward travel stop (118) contacts the bushing
(126). The apparatus is then in its equilibrium state (center
point).
Rightward Displacement of the Control Rod
When the control rod (102) is forced to the right, the bushing
(126) is consequently forced to the right due to contact with the
rightward travel stop (118). Because the rightmost support bracket
(116) is stationary, rightward movement of the bushing (126)
results in compression of the leftmost spring (112) in proportion
to the rightward displacement of the control rod (102). Because the
rightmost preload device (120) moves with the bushing (126), the
rightmost spring (122) remains constant and unaffected in its
preload state. When the external actuating force is removed from
the control rod (102), the increased spring pressure in the
leftmost spring (112) forces the bushing (126) back to the left
until the leftward travel stop (108) contacts the stationary
support area (106). Since the bushing (126) is always in contact
with the rightward travel stop (118) which is in turn fixed to the
control rod (102), the control rod (102) is forced to move leftward
in synchronous travel with the bushing (126).
Construction of the Apparatus
The present embodiment allows for use of materials suitable for any
particular application. For example, the control rod (102) must be
manufactured from a material or materials with qualities that can
withstand the types of forces that it will encounter. In the
present embodiment, the control rod (102) is made of metal. The use
of metal affords durability, strength, rigidity, and machineability
over softer materials, and allows the control rod (102) to
withstand compressive and tensile stresses experienced in
operation. However, other materials, such as plastic or plastic
composites may be used so long as the rod is capable of
withstanding the environmental extremes in which it operates. Any
suitable material may be utilized without exceeding the scope of
the present invention.
The shape of the control rod (126) in the present embodiment is
cylindrical. However, other cross-sectional shapes (such as a
triangular, square, rectangular, or oval) may be utilized depending
on the application requirements. For example, a particular
cross-section shape may provide additional rigidity in a particular
application and may be preferable over a standard circular cross
section. Any suitable shape may be utilized without exceeding the
scope of the present invention.
Likewise, the bushing (126) is made of metal to withstand,
primarily, the compressive stresses it encounters in operation. The
material chosen should be sufficiently durable, rigid, and
machineable to prevent undue deflection or distortion of the
bushing (126). This is important because the control rod (102) must
be free to move within the bushing (126), relative to the bushing
(126). In addition, the bushing (126) must be free to move within
the brackets (104 and 116), relative to the brackets (104 and 116).
Any such suitable material may be utilized without exceeding the
scope of the present invention.
The shape of the bushing (126) in the present embodiment is
cylindrical. However, other cross-sectional shapes (i.e.,
triangular, square, rectangular, oval, etc.) maybe utilized
depending on the application requirements. For example, a
particular cross-section shape may provide additional rigidity in a
particular application and may be preferable over a standard
circular cross section. Any suitable shape may be utilized without
exceeding the scope of the present invention. If a different shape
is utilized, the openings in the brackets (104 and 116) through
which the bushing (126) must pass must correspond. Likewise, the
central opening in the bushing (126) through which the control rod
(102) must pass must also correspond with the control rod (102)
cross-sectional shape.
The brackets (104 and 116) in the present embodiment are metal and
are designed to provide adequate support to the overall device. The
brackets (104 and 116) are also sufficiently rigid to allow the
springs to operate without undue deflection. The shape and
materials of the brackets (104 and 116) are immaterial and any
shape or material chosen is within the scope of the present
invention.
To improve the operation of the present invention, certain coatings
or lubricants may be utilized on the material surfaces. For
example, the bushing (126) may utilize soft-metal or polymer
coatings on its inner and/or exterior friction surfaces. Further,
such friction reducing materials may be utilized on the control rod
(102) and/or bracket (104 and 116) friction surfaces as well. Use
of friction reducing materials is within the scope of the present
invention.
The present embodiment features the use of an adjustable collar
(124) as an attaching means for attaching the spring (122) to the
control rod (102). It will be appreciated that other attaching
means, such as clamps, threaded nut, welded washers, a machined
feature, or the like, may be employed without departing from the
scope of the present invention. For example, another embodiment of
the present invention may feature a washer-type shape welded to the
control rod, against which the spring force is applied. The present
invention merely dictates that an attaching means be supplied that
is sufficient to maintain contact between the spring and the rod.
The scope of the present invention is intended to encompass all
equivalent structures.
While the present embodiment utilizes an adjustable collar for the
rightward travel stop (118), other means, such as a clamp, threaded
nut, welded washer, machined feature, or the like, may be used
without departing from the scope of the present invention. The
means chosen for the travel stop (118) must be suitable to maintain
contact between the control rod (102) and the bushing (126),
without slippage of the stop (118) due to impact by the bushing
(126). The scope of the present invention is intended to encompass
all equivalent structures.
This embodiment uses a nut for a leftward travel stop (108).
However, other means, such as a clamp, welded washer, machined
feature, or the like, may be utilized for the stop (108) and are
within the scope of the present invention. For example, the support
area (106) on the leftmost bracket (104) may have a machined flange
that serves as the leftward travel stop.
Two different locknuts (110 and 120) are featured in the present
embodiment. These locknuts (110 and 120) are attached to the
bushing (126) in two distinct locations. These adjustable locknuts
serve as spring preload devices. While the present embodiment
utilizes adjustable nuts (110 and 120) for the preload devices,
other means may be utilized and are within the scope of the present
invention. For example, the rightmost end of the bushing (126) may
feature a raised machined flange against which the rightmost spring
(122) may abut. Likewise, the leftmost nut (110) could be replaced
with a similar welded or machined flange against which the
rightmost spring (112) abuts and against which the leftward travel
stop (108) would impact.
One important aspect of the invention is the precision which can be
obtained in centering the control rod (102). This is primarily due
to the fact that the left and right springs (112 and 122) may be
independently adjusted to establish preload. The positive stops
(118 and 108) dictate the control rod (102) center point
independent of the spring preload. Left spring (112) preload
ensures the leftward travel stop (108) remains seated against the
stationary support area (106). Right spring (122) preload ensures
the rightward travel stop (118) remains seated against the bushing
(126), which is stationary because the leftward travel stop (108)
is seated against the stationary support area (106). A change in
preload on either the right or left springs will only serve to vary
the external force required to actuate the control rod (102) in the
rightward or leftward direction.
To adjust the control rod (102) center point, loosen the right
spring attaching means (124) to remove the right spring (122)
preload pressure. If the attaching means (124) is not adjustable,
the rightmost preload device (120) can be adjusted instead. Next,
loosen the rightward travel stop (118). While maintaining the
leftmost travel stop (108) seated against the stationary support
area (106) and the rightmost travel stop (118) seated against the
bushing (126), position the control rod (102) as necessary. Next,
tighten the rightward travel stop (118) while maintaining contact
with the bushing (126). Restore right spring (122) preload by
repositioning the attaching means (124) and reestablishing proper
preload by adjusting the rightmost preload device (120).
The invention may be embodied in other specific forms without
departing from the spirit or essential characteristics thereof. The
present embodiments are therefore to be considered in all respects
as illustrative and not restrictive, the scope of the invention
being indicated by the appended claims rather than by the foregoing
description, and all changes which come within the meaning and
range of equivalency of the claims are therefore intended to be
embraced therein. Further, the recitation of method steps does not
denote a particular sequence for execution of the steps. Such
method steps may therefore be performed in a sequence other than
that recited unless the particular claim expressly states
otherwise.
* * * * *